The present invention relates to a component assembly as well as to a method for producing a component assembly.
Electronic and/or optoelectronic components may be placed on carrier substrates, such as circuit boards in several ways. It is customary, for instance, for unhoused components to be initially placed on the circuit board at a designated location and subsequently electrically contacted, for example by wire bonding. An injection needle or a so-called dispenser is subsequently used to position an enclosed dam on the circuit board to surround the component. Finally, in a further process step, a suitable encapsulating material is introduced into the well-shaped inner region of the dam, so that the component and any existing bonding wires, etc., are covered by the encapsulated material and protected from environmental influences. In connection with component assemblies of this kind, reference is made, for example, to German Published Patent Application No. 195 30 878 and Japanese Published Patent Application No. 61-101054. From both documents it can be inferred, that the dam has two dam layers.
A number of problems arise in the context of high component densities, as well as with regard to the use of electronic components. Thus, in component assemblies of this kind, a smallest possible base area must be ensured for the dam on the particular carrier substrate, in order not to needlessly cover essential space on the carrier substrate. A two-part dam structure discussed in German Published Patent Application No. 195 30 878 requires, for example, a relatively large base area for the dam on the carrier substrate, and therefore, does not fulfill this requirement.
In addition, the use of optoelectronic components requires that the encapsulating material placed over this component have, to the extent possible, no undesired optical effect for the beam of rays passing through. This is also not ensured in the case of German Published Patent Application No. 195 30 878, since the beam of rays passing through is deflected at the curved boundary surface between the encapsulating material and the ambient air due to the resulting lens effect.
It is also to be noted in connection with the assembly described in Japanese Published Patent Application No. 61-101054 that the two dam layers having different melting points require considerable costs for process control due to the different processing temperatures. Expenses are also entailed in terms of process technology, due to the necessity to process a plurality of dam materials in the manufacturing of such an assembly.
An object of the present invention is, therefore, to provide a method for the manufacture of a component assembly which satisfy the specific requirements. In particular, besides a greatest possible component density and adequate mechanical stability, an object of the present invention is to also ensure the usability of optoelectronic components. Also desirable is a simplest possible manufacturing of a component assembly of this kind.
This objective is achieved by providing a method as described herein.
The measures in accordance with the present invention may ensure that a stable bond forms in the contact region between adjacent dam layers. When a suitable dam material is used, there is a stable cross-linking of the two adjacent dam layers in this region. The stable bond in this region results in a mechanically more resistant overall assembly. It is thereby possible to form high dams having a comparatively small dam surface area, i.e., high component densities are also able to be ultimately realized in accordance with the present invention. Due to the possible high dam structure, the inner region of the dam may be filled with a suitable encapsulating material such that this material has a virtually ideal, plane surface area. No undesired, optically deflecting action results at the boundary surface with the ambient air for the beam of rays passing through. As discussed above, this may be an essential requirement when optoelectronic components are to be used in assemblies of this kind.
The use of the identical dam material in all dam layers also signifies that all dam layers have the same thermal expansion coefficient. Therefore, no thermally induced stresses may occur between the various dam layers in the dam.
Also, from a standpoint of production engineering, a number of advantages may be derived from the measures according to the present invention. Thus, in contrast to the above-mentioned Japanese Published Patent Application No. 61-101054, the need is eliminated to keep different materials available for the minimum of two dam layers, since the at least two dam layers are made of the same material. In addition, in the various process steps in which the various dam layers are applied, there is no longer a need to have different temperatures due to different melting points or processing temperatures.
Due to the use of the same material in the dam layers, a stable bond may be ensured. Thus, for instance, when using suitable material, a chemical cross-linking results in the contact region upon final curing. The result is a high mechanical load-bearing capacity of the dam.